Circuit interrupters are electrical components that can be used to break an electrical circuit, interrupting the current flow. A basic example of a circuit interrupter is a switch, which generally consists of two electrical contacts in one of two states; either closed, meaning that the contacts are touching and electricity can flow between them, or open, meaning that the contacts are separated, and no electricity can flow between them. A switch may be directly manipulated by a human to provide a control signal to a system, such as a computer keyboard button, or to control power flow in a circuit, such as a light switch.
Another example of a circuit interrupter is a circuit breaker. A circuit breaker may be used, for example, in an electrical panel to limit the electrical current being sent through the electrical wiring. A circuit breaker is designed to protect an electrical circuit from damage caused by an overload or a short circuit. If a fault condition such as a power surge occurs in the electrical wiring, the breaker will trip. This will cause a breaker that was in the “on” position to flip to the “off” position and shut down the electrical power leading from that breaker. When a circuit breaker is tripped, it may prevent a fire from starting on an overloaded circuit; it can also prevent the destruction of the device that is drawing the electricity.
A standard circuit breaker has a terminal connected to a power supply, such as a power line from a power company, and another terminal connected to the circuit that the breaker is intended to protect. Conventionally, these terminals are referred to as the “line” and “load” respectively. The line may sometimes be referred to as the input into the circuit breaker. The load, sometimes referred to as the output, feeds out of the circuit breaker and connects to the electrical components being fed from the circuit breaker.
A circuit breaker may be used to protect an individual device, or a number of devices. For example, an individual protected device, such as a single air conditioner, may be directly connected to a circuit breaker. A circuit breaker may also be used to protect multiple devices by connecting to multiple components through a power wire which terminates at electrical outlets, for example.
A circuit breaker can be used as a replacement for a fuse. Unlike a fuse however, which operates once and then must be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Fuses perform much the same circuit protection role as circuit breakers. However, circuit breakers may be safer to use in some circumstances than fuses, and may be easier to fix.
For example, in a situation where a fuse blows, interrupting power to a section of a building for example, it may not be apparent which fuse controls the interrupted circuit. In this case, all of the fuses in the electrical panel would need to be inspected to determine which fuse appears burned or spent. This fuse would then need to be removed from the fuse box, and a new fuse would need to be installed.
In this respect, circuit breakers can be much simpler to use than fuses. In a situation where a circuit breaker trips, interrupting power to a section of a building for example, it may be easily apparent which circuit breaker controls the interrupted circuit by looking at the electrical panel and noting which breaker has tripped to the “off” position. This breaker can then be simply flipped to the “on” position and power will resume again.
In general, a typical circuit interrupter has two contacts located inside of a housing. The first contact is stationary, and may be connected to either the line or the load. The second contact is movable with respect to the first contact, such that when the circuit breaker is in the “off” or tripped position, a gap exists between the first and second contact.
A problem with circuit interrupters that operate by separating contacts arises because the energized contacts separate when the circuit breaker is tripped, causing a gap to widen between the contacts while the movable contact moves from the closed position to the open position.
As the contacts begin to separate from the closed position, or approach complete closure from an open position, a very small gap exists between the contacts for a brief time while the contacts are closed or opened. An electric arc may be generated across this gap if the voltage between the contacts is high enough. The creation of an arc during switching or tripping the circuit interrupter can result in undesirable side effects which can negatively affect the operation of the circuit interrupter, and which can create a safety hazard.
These effects can have consequences for the operation of the circuit interrupter. One possible consequence is that the arc may short to other objects in the circuit interrupter and/or to surrounding objects, causing damage and presenting a potential fire or electrocution safety hazard. In particular, the arc can damage the escapement, which comprises a part of the linkage that opens and closes the contacts.
Another consequence of arcing is that the arc energy damages the contacts, causing some material to escape into the air as fine particulate matter. The debris which has been melted off of the contacts can migrate or be flung into the mechanism of the circuit interrupter, destroying the mechanism or reducing its operational lifespan.
Another effect of arcing stems from the extremely high temperature of the arc (tens of thousands of degrees Celsius) which can crack the surrounding gas molecules creating ozone, carbon monoxide, and other compounds. The arc can also ionize the surrounding gasses, potentially creating alternate conduction paths.
Various techniques have been used in an attempt to mitigate the dangers associated with arcing. For example, it has been known to try and direct the arc toward arc quenching devices. However, the construction, configuration and placement of the moving parts of the circuit interrupter have left the escapement particularly vulnerable to damage caused by arcing.
Likewise, known configurations for circuit interrupters have previously included a handle external to the circuit interrupter, a catch and an escapement coupled to the handle, and a moveable contact arm positioned substantially perpendicular to the catch and escapement. While this configuration is effective in opening and closing the contacts, this configuration does place the moveable contact arm in the vicinity of any arc that is generated. Likewise, this design requires an increased number of moving parts making the device more expensive to manufacture and more timing intensive to assemble, and increases the weight of the device, which can be critical in certain applications.
It is therefore desired to provide an alternative construction for a circuit interrupter that overcomes these limitations.